It is known in the state of the art that macular pigment in particular has a positive effect in preventing AMD because it acts as an absorber for high-energy shortwave radiation and therefore protects the area of sharpest vision from damage. At the same time, macular pigment, containing primarily the carotinoids lutein and zeaxanthin, functions as a radical scavenger. A low optical density of the macular pigment is a risk factor for the development of age-related macular degeneration. Since lutein and zeaxanthin are not formed in the human body but instead must be ingested with food, it is necessary to determine the individual optical density of the macular pigment to detect a possible risk on this basis and to ascertain whether there is a need for supplementation of lutein and zeaxanthin.
For a reliable diagnosis of the disease and/or the risk of developing AMD, it is therefore necessary to determine very accurately and without stray light the density of the macular pigment, which is formed in layers in front of the object to be examined, specifically the ocular fundus. These scattering effects caused by the lens of the eye in particular increase with age, so that the determination of the optical density of the macular pigment on the ocular fundus, which is a known method per se, is increasingly impaired due to scattering effects with the advancing age of the patient. Accurate determination of the optical density of the macular pigment is also important for the decision about the need for and detection of the success of the aforementioned supplementation with lutein and zeaxanthin.
According to the state of the art, it is also known that digital photographs of the retina can be prepared using ophthalmologic instruments, e.g., fundus cameras, ophthalmoscopes or slit lamps. Photographs of the fundus make it possible to determine the optical density of the macular pigment (macular pigment optical density=MPOD or also just MPD).
DE 101 29 652 A1 thus describes one approach in which the ocular fundus is illuminated with light of a wavelength range in which macular pigment has maximum absorption. A shading function is determined from the light intensity that can be measured outside of the macular area (containing no macular pigment). To calculate the optical density of the macular pigment, the quotient of the calculated value of the shading function and the measured intensity value of the light reflected from the illuminated ocular fundus is calculated for each pixel in the area of the macula. The shading function indicates virtually the reflected light that would be reflected by the ocular fundus in the area of the macula if no macular pigment were present.
U.S. Pat. No. 7,467,870 B2 relates to an instrument for highly precise determination of the macular pigment in a patient's eye. The eye is therefore illuminated with a broadband light, and the light reflected by the ocular fundus is then analyzed with the help of a spectrometer. The spectral analysis makes it possible to better differentiate the macular pigment from other light-absorbing substances such as lipofuscin. Since this instrument operates without dilating the pupils, additional measures are necessary to minimize unwanted reflection. In addition to anti-reflection coatings on lenses, a strict separation of the illumination path and the scanning beam path and also an offset arrangement of the lenses are provided in this approach, so that the beam paths additionally pass through the lenses decentrally. According to the setup described in U.S. Pat. No. 7,467,879 B2, measurements are not performed with local resolution but instead are integrated over the illumination and detection area of the retina. It is proposed that the patient's eye should be refocused for peripheral measurements. This makes it possible to determine the lateral distribution of the macular pigment.
It has been found that increased scattering in the eye caused by age-related clouding of the ocular media can lead to a lower measured value for the optical density of the macular pigment. If the light scattering in the lens of the eye also exhibits a great dependence on wavelength, then the density of the macular pigment is calculated as being too high with an increase in scattering even in the two-wavelength fluorescence method (“Macular pigment density measured by autofluorescence spectrometry: comparison with reflectometry and heterochromatic flicker photometry” in Delori et al., J. Opt. Soc. Am. A, Vol. 18, No. 6, June 2001).
Several of the approaches in the state of the art, such as DE 10 2005 058 185 A1, DE 10 2007 025 425 A1 and DE 10 2004 042 198 A1, for example, have been concerned with correctly determining the measured values of the optical density of the macular pigment and/or with the corresponding compensation of the measurement errors.
DE 10 2007 047 300 A1 also describes an approach for accurate reflectometric determination of the optical density of the macular pigment on the ocular fundus without any influence due to interfering light, in particular due to individual light scattering on the anterior ocular media. In addition to measuring the reflected light from illuminated areas of the ocular fundus, the latter is instead illuminated only partially and the intensity of the interfering light from the unilluminated area is measured. This measured value is used as a correction factor in calculating the optical density of the macular pigment.
According to the state of the art, the following parameters are extracted from the measurement of the optical density of the macular pigment, for example:                mean and maximum concentrations,        the area and        the volume of the macular pigment (in the sense of the surface integral of the macular pigment density).        
These parameters are used by ophthalmologists in addition to other diagnostically relevant test results to be able to assess the risks of developing a certain disease, e.g., dry AMD and/or to track and assess the course of this eye disease.